1. Field of the Invention
The present invention relates to a process for producing distilled liquors having an excellent flavor by the use of yeast into which a ferulic acid decarboxylase gene has been introduced.
Ferulic acid decarboxylase is an enzyme which catalyzes the decarboxylation of ferulic acid to form 4-vinylguaiacol.
2. Brief Description of the Background Art
In the liquor industry, it is always desired to develop distilled liquors such as shochu (a Japanese distilled liquor), bai jiu (a Chinese distilled liquor), whiskey, brandy, vodka, rum, gin and the like having an excellent flavor. Distilled liquors possesing an excellent flavor typically have a relatively high content of at least one of 4-vinylguaiacol, vanillin, or vanillic acid.
Vanillin and vanillic acid are formed by oxidation of 4-vinylguaiacol Nippon Nogeikagaku Kaishi, 70(6), 684-686 (1996)!.
It is known that distilled liquors having an excellent flavor can be produced by adding hydroxycinnamic acid ester hydrolase, or a koji mold having a high productivity of hydroxycinnamic acid ester hydrolase, (Japanese Published Unexamined Patent Application No. 115957/95) or ferulic acid esterase Nippon Nogeikagaku Kaishi, 70(6), 684-686 (1996)! to liberate ferulic acid into moromi.
Ferulic acid, as well as cinnamic acid and coumaric acid, is a kind of phenylacrylic acid, and is bonded in the form of ester to the arabinose side chain of arabinoxylan contained in the hemicellulose fraction which constitutes cell walls of plants such as cereals.
A method for preparing yeast having a high ferulic acid decarboxylase activity by cell fusion has been proposed Abstracts of the Annual Meeting of the Society of Fermentation and Bioengineering, 41 (1995)!. However, it has not yet been possible to obtain yeast having an increased ferulic acid decarboxylase activity. Accordingly, a method of producing distilled liquors having an excellent flavor by the use of such yeast is not known.
Ferulic acid decarboxylase of Bacillus pumilus Appl. Environ. Microbiol., 61(1), 326-332 (1995)! and that of Pseudomonas fluorescens J. Bacteriol., 176, 5912-5918 (1994)! have already been isolated and purified. The gene encoding ferulic acid decarboxylase (hereinafter referred to as FDC gene) of B. pumilus Appl. Environ. Microbiol., 61, 4484-4486 (1995)! is also known. Ferulic acid decarboxylase of yeast belonging to the genus Saccharomyces, etc. has not been isolated, even though the existence of the enzyme activity has been recognized.
As to Saccharomyces cerevisiae, the gene encoding phenylacrylic acid decarboxylase (hereinafter referred to as PAD1 gene) Gene, 142, 107-112 (1994)! is known, but there is no report on its FDC gene.
An object of the present invention is to provide ferulic acid decarboxylase which is useful in the production of distilled liquors having an excellent flavor.